Process for producing high quality white petroleum oil with sulfuric acid followed by sulfuric acid and formaldehyde



| I l i l 1 6, 1958 E. RUNDALE ETAL ,84

PROCESS FOR PRODUC NG HIGH QUALITY WHITE PETROLEUM OIL WITH SULFURIC ACID FOLLOWED BY SULFURIC ACID AND FORMALDEHYDE Filed June 17, 1954 H 12 (l6 I8 13 l7 low FEED T f L u STORAGE l :I-- DISTILLATION/ H kl5 j,|9

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i T 32 l T 26 1 20 T 24 33 WASHING L5? ACID 22 ACID ZONE TREATING TREATING l l ZONE l ZONE WASHING 35 H FILTER ZONE ERVING ARUNDALE JOSEPH VERSTEEG} 'NVENTORS ATTORNEY United States Patent @fiice 2,849,375 Patented Aug. 26, 1958 PROCESS FOR PRODUCING HIGH QUALITY WHITE PETRQLEUM OIL WITH SULFURIC ACID FOLLOWED BY SULFURIC ACID AND FURMALDEHYDE Erving Arundaie, Westfield, and Joseph Versteeg, Elizabeth, N. 3., assignors to Esso Research and Engineering Company, a corporation of Delaware Application June 17, 1954, Serial No. 437,395

Claims. (Cl. 196-40) This invention relates to a process for producing high quality petroleum oils, and more particularly to a process for producing White oils having a low content of aromatics and at the same time being reasonably free of malodorous compounds. In the past, when producing white oils, it has been customary to treat the petroleum distillate with concentrated sulfuric acid in a succession of treating steps referred to in the art as dumps. According to the conventional method, the untreated oil is intimately mixed with 98% sulfuric acid at room temperature, allowed to stand until a sludge is formed, and then the supernatant liquid is separated from the sludge and treatment of the oil is repeated. This procedure is repeated from two to five times.

In order to produce an oil having a sufficiently low aromatic content and possessing a satisfactory odor to make it acceptable to the trade, it has heretofore been found necessary to carry out the last treating step or dump using fuming sulfuric acid or oleum having a sulfuric acid concentration of from 105% to 107% H 80 by weight. Although the use of this material in the final step results in the production of a satisfactory oil, a number of serious disadvantages have been found to be incident to the use of this fuming sulfuric acid. Primary amongthese disadvantages is the danger to the health of personnel handling the acid because of the fumes associated with its use. Accordingly, elaborate and expensive safety precautions must be taken in order to employ the method of the prior art. In addition, fuming sulfuric acid is substantially more expensive than the 98% acid used in the initial treating steps, and it has also been found that larger amounts of sulfuric acid by weight are necessary in the final dump than in any of the previous steps, with the result that losses of oil to degradation products are excessive.

The term white oil as used herein refers especially, but not exclusively, to that type of refined petroleum oil generally known to the trade as deodorized waterwhite or deodorized kerosene, a highly treated, closecut oil possessing a distillation range of approximately 400 F. to 500 F. at atmospheric pressure, as compared with a range of about 330 F. to 560 F. for ordinary kerosene as marketed for fuel purposes. Deodorized oils of this type are employed largely in the production of liquid insecticide sprays such as are used for the extermination of flies, moths, bed bugs, roaches and other common insects. In such capacity the deodorized waterwhite type of product is preferred over ordinary kerosene because of its higher flash point, freedom from objectionable odor, and absence of the higher boiling fractions or heavy ends which lead to staining problems when insecticides prepared from ordinary kerosene are sprayed onto household furnishings or clothing.

It is not intended, however, that this invention be limited specificaliy to the production of refined petroleum oils falling within the distillation range of kerosene, as already noted, but the process substantially as described may be extended to include the treatment and deodorization of higher boiling petroleum distillates such as are used for the production of the more viscous white oils. Such products find numerous uses in the trade, a few of which include the manufacture of stock sprays, horticultural sprays, cosmetic and hair oils, food processing oils, pharmaceutical products, lubricants, etc. They are produced in a wide variety of viscosities ranging from around 45 seconds Saybolt to about 350 seconds Saybolt at 100 F. Such oils are colorless or nearly so, and further characterized by the absence of aromatics, olefins and malodorous substances, all of which it is the object of this invention to remove from the untreated distillate to the extent that the finished white oil will be acceptable to the trade.

It is an object of this invention, therefore, to provide a method for producing high quality white oils which are equivalent in aromatic content, API gravity, and odor to those oils produced when treating petroleum oils by conventional methods, but without the use of fuming sulfuric acid.

It is a further object of the invention to provide a method for making a white oil having properties acceptable to the trade that utilizes sulfuric acid containing not more than about 98% H 50 it is a still further object of this invention to produce a white oil equivalent to that of the prior art at a substantially lower cost, with reduced losses to degradation products, and under conditions substantially less hazardous to personnel than those of the prior art process.

These and other objects, which will be in part pointed out and in part apparent in the subsequent description, are attained through the use of a method which comprises contacting a petroleum distillate in one of a plurality of acid treating steps with an acid mixture comprising more than about 90% and less than about 98% by weight of sulfuric acid based on the weight of the acid mixture, and at least about 0.1% of formaldehyde based on the weight of the oil being treated. It has been found that by substituting such a mixture of sulfuric acid and formaldehyde for the conventional fuming sulfuric acid, a product equal in quality to that produced by the prior art methods can be made.

In U. S. Patent No. 2,567,175 to Erving Arundale and Edwin E. Juterbock, a process is described for the treatment of virgin distillates with a mixture of sulfuric acid and formaldehyde in order to remove mercaptans. That patent points out that it is essential to use a relatively dilute sulfuric acid containing less than 90% H by weight in order to avoid the removal of aromatics through reaction with formaldehyde. Loss of aromatic hydrocarbons from gasoline distillates would result in a loss in octane number. In contrast to that process, it has been found that the present process for producing saleable white oils requires the use of acid containing more than about H 80 by weight in order to lower the aromatic content of the material to the desired level, and to produce an oil having a satisfactory odor.

The process of the present invention may be more readily understood by reference to the drawing illustrating an embodiment of the same.

Referring now specifically to the drawing, a feed oil,-

means of line 13. Fractions boiling at temperatures above the desired range are removed from zone by means of lines 14 and 15, depending upon the boiling point.

In accordance with-conventional practice, the hydrocarbonfraction boiling withinthe desiredrauge is condensed and passed into a storage, zone;1 6. This fraction is removed from. the storage zone .16 -.by means of line 17 and contacted with 98% sulfuric-acid introduced into line .17 by means of line 18. Mixingis secured: by the orifice mixer 19 or by equivalent means. The oil and acid are introduced into the separationzone 20 through line 21 and there separate into-a heavyspent acid phase mixed with sludge, whichis removed ,at22, anda light oil phase, which is removed through, line .23. A mixture of concentrated-sulfuric acid containing between 90% and 98% sulfuricvacid by weight and formaldehyde, preferably in the form of a water solution thereof, is introduced through line 24 and mixing of these two constituents .is carried .out in. the orifice mixer 25 or by equivalent means. This mixture is introduced into the secondsettling zone,. or dump, 26, wherein it separates into a heavyphase of sludge and spent acid, which is removed through line .27, and a light treated oil phase, which is removed through 28.

Itwill be understood, of course, that this drawing represents only one embodiment of the invention, namely, that in which only two acid dumps, i. e., two acid addition and settling steps which take place in zones 20' and 26, occur. In other embodiments of the invention a greater number of dumps employing 98% acid may be employed. In other words, instead of a single settling zone corresponding to 20, there may be two, three, four, or more suchzones in series prior to the final step in which the more dilute acid and formaldehyde are introduced.

The spent oil leaving zone 26 through line 28 may then be mixed wtih a caustic solution introduced through line 29 and mixed therewith in the orifice mixer 30. The mixture of oiland caustic passes through line 31 to the settling zone 32, wherein it separates into a spent caustic phase and a washed oil phase. The heavier caustic is removed through line 33 and the washed oil, which has beenfreed of acid by this operation, passes through line 34 to washing zone 35, wherein it is washed with water introduced through line 36 to remove caustic. The water and caustic phase is removed through line 37 and the washed oil removed through line 38. In some embodiments of the invention a filtering step through a medium such as fullers earth may take place in the filter 39 before discharging the finished oil through line 40 for appropriate storage or packaging for use.

The starting material for the present process may be any petroleum distillate, preferably a virgin distillate, boiling in the range of about 300-750 F. containing an undesirably high concentration of aromatics, olefins, and malodorous compounds, which is otherwise suitable for the production of white oil. The boiling range of this distillate is usually within the somewhat narrower range of 400-600 F., and most preferably from about 400 F. to 500 F. This feed stock is mixed with 98% sulfuric acid in the amount of from about 5 to about pounds of acid per barrel of feed stock (depending on the content of undesirable substances), and is contacted for about an hour at ambient temperature and pressure in the same manner as employed by prior art processes. There appears to be no advantage in operating at elevated temperatures and/ or pressures. The sludge formed by this treatment is then separated from the supernatant liquid and the liquid is then subjected to an additional acid treating step, in which the same proportion of acid to feed is normally employed. This process may be repeated again; the total number of dumps normally varies between two and five.

During ,one'ofthe treating steps, formaldehyde, preferably in the,form of e37 weight percent aqueous solution, is added to the 98% sulfuric acid, and this mixture is contacted with the partially treated oil in the same proportions as used in the previous treating steps. For most oils, this will amount to about 25 pounds of acid per barrel of feed. As will be illustrated by a subsequent example, it is preferred that the formaldehyde be added :in the last acid treatment only. Due to the addition of water from the aqueous solution, the concentration-of the-acid-used in this final step is reduced to below the original value of 98%. It is essential, however, that the effectiveconcentration of the sulfuric acidv in this treatingstep bemaintained at a value about by weight. If. theacidisdiluted beyond this value, it will berelatively ineifective for removing aromatics and for improving the odor of the oil.

It has been foundsthat the. concentration of forma dehyde used in the final treating step must be at least about 0.1% based on the weight of the feed in order that.results equivalent to those obtained from using fuming sulfuric acid be obtained. On the other hand, there is little advantage in the inclusion of formaldehyde in amountsmuch greater than this, since the degree of improvement of product quality is not commensurate with the added expense. Another factor limiting the maximum amount of formaldehyde to be added is the fact that it ispreferably introduced as an aqueous solution, thus diluting the acid. When using formaldehyde in the form ofan aqueous solution, itis necessary that the amount of formaldehyde solution added in the last treating step be such that the water so introduced will not dilute the acid below its effective value, i. e., about 90%. When an aqueous solution of 37% by Weight of formaldehyde is used, the addition of more than about 0.4% by weight of formaldehyde based on weight of oil dilutes the acid to below the desired concentration. It will be understood, of course, thatformaldehyde may be introduced in its anhydrous form as paraformaldchyde, although better contact with the acid and oil is obtained using an aqueous solution. When using paraformaldehyde, no dilution problem exists, but even in such cases it is not desirable to .add more than about 2% of formaldehyde based on the weight of oil.

In order .to produce a satisfactory commercial product, it has been found that five acid treating steps or dumps are required. According to. conventional prior art processes this would mean four dumps using 98% acid and a final dump using fuming sulfuric acid. According to the preferred method of the present invention, four dumps of 98% acid are used, followed by a final dump of acid containing formaldehyde.

Following the separation of the sludge formed in the final acid treatment, the product is washed with 10-20 volume percent of 5% sodium hydroxide solution, followed by a wash with 10-20 volume percent of Water. It will be understood, of course, that either more or fewer than five acid treating steps may be employed, depending upon the properties of the oil being treated and upon the characteristics desired in the final product with respect to odor, content of aromatics (as expressed in terms of aniline point), and API gravity. In any event, it will be found that an acid mixture containing between 90 and 98% sulfuric acid by weight and at least about 0.1% formaldehyde based on the weight of the oil treated will be equivalent in effect to the use of fuming sulfuric-acid, and that furthermore a much smaller weight of such a solution will be equally effective as a considerably larger weight of the fuming acid.

The process of the present invention may be illustrated by the following examples:

EXAMPLE I A virgin petroleum distillate boiling between 400- 504 F. and possessing an API gravity of 453 and an aniline point of 163.4" E, was subjected to four successive acid treatments at .room temperature employing 98% sulfuric acid, in which each acid treatment utilized 25.4 pounds of sulfuric acid per barrel of feed distillate, with a contact time of one hour and with sludge separation between treats. Following these four treatments, fuming sulfuric acid (containing 107% H SO by weight) was added in the amount of 41.8 pounds of sulfuric acid per barrel of distillate being treated. After final sludge separation and after water and caustic washing, it was found that the white oil made by this treatment had an aniline point of 1778' F. and an API gravity of 48.5. This pro-duct was further found to have the lowest possible odor rating. 14.6 volume percent of the original feed was lost to sludge in this process.

The aniline point may be defined as the temperature at which aniline and the treated material become miscible. This temperature is inversely proportional to the aromatic content of the oil, so that as high an aniline point as 11132531311: is desired in white oil production, usually above EXAMPLE II The same feed stock as employed in Example I was subjected to four successive acid treatments identical with those described above, and was then given a final acid treatment with an acid mixture containing 96.5% sulfuric acid by weight and 0.1% by weight formaldehyde (added as 37% by weight of aqueous solution) based upon the amount of feed stock being treated. The acid in the last treating step was added in the amount of 25.4 pounds of 98% acid per barrel of feed stock. This is to be contrasted with the 41.8 pounds of fuming sulfuric acid used per barrel of feed stock in Example I. The oil produced by using 0.1% formaldehyde in the final treating step had an aniline point of 176.7 and an API gravity of 48.1. Its odor rating was the same as that of the oil produced according to the conventional method described in Example I, but the loss was 1.5% lower. When the conditions of Example II were duplicated but formaldehyde was not added in the fifth 98% acid treat, a product of inferior odor was obtained. Therefore, it will be seen that the method of the present invention gives a white oil having properties substantially equivalent to those of conventionally treated white oil, and that the use of formaldehyde in the final treating step permits the employment of a more dilute, safer, and cheaper sulfuric acid mixture and also a substantially smaller weight of sulfuric acid. This substitution results in a considerable economy.

EXAMPLE III The same feed stock as used in the previous example was treated in exactly the same way, except that the formaldehyde concentration in the last step was 0.25 weight percent based on feed, and the effective acid strength of this mixture was therefore 93.7%. The oil produced by this treatment had an aniline point of 176.7 and an API gravity of 48.1, just as the oil produced according to the method described in Example II. The odor of the oil produced was also equivalent to that made by prior art processes.

EXAMPLE IV The treatment described in the previous two examples was repeated, except that an additional amount of aqueous formaldehyde solution was added in the last treatment so that it had an effective acid strength of 91.5% sulfuric acid by weight and contained 0.4% by weight of formaldehyde based on the weight of the feed. The oil produced by this treatment had an identical aniline point and API gravity with those produced by the method of Examples 11 and III. However, the odor of this oil, while entirely acceptable, was not quite as good as that made by using slightly higher effective acid concentrations in the last step. It is considered, therefore, that this composition represents about the maximum formaldehyde concentration that can be employed when using a 37% solution of formaldehyde in water to produce a satisfactory substitute for fuming sulfuric acid in this process. Above this point, dilution of the acid with water from the aqueous formaldehyde solution becomes excessive and the acid is therefore less efiective.

EXAMPLE V In the preferred embodiment of the invention, the formaldehyde is included in the final acid treating step rather than in the initial or in any of the intermediate steps. The advantages of employing formaldehyde in the last step are illustrated by the data set forth in Table I below.

In addition to the higher aniline point, it should be noted that the sample utilizing 0.25 weight percent formaldehyde in the last of five dumps had the best odor of the oils in the table.

While there have been described above a number of specific embodiments of the process, it will be understood that the present invention is not limited thereby, but embraces those equivalents which will occur to those skilled in the art.

What is claimed is:

1. In the process of producing a high quality petroleum white oil wherein a virgin petroleum distillate boiling in the range of from about 300 to 750 F. is subjected to a succession of sulfuric acid treating steps, the improvement which comprises treating said distillate with 98 percent sulfuric acid in each of said steps with the exception of the final step, and treating said distillate in the final step with an acid mixture comprising more than about percent and less than 98 percent of sulfuric acid, based on the weight of said mixture, and from about 0.1 percent to about 0.4 percent of formaldehyde, based on the weight of said distillate.

2. The process as defined by claim 1 wherein four successive treats with 98 percent sulfuric acid are employed, followed by a fifth treat utilizing said mixture of sulfuric acid and formaldehyde.

3. The process as defined by claim 2 wherein said fifth 'treat involves treatment with a mixture comprising sulfuric acid of about 96.5 percent strength and sufficient formaldehyde to equal about 0.1 percent formaldehyde based on the weight of said distillate.

4. The process as defined by claim 2 wherein said fifth treat involves treatment with a mixture comprising sulfurie acid of about 93.7 percent strength and suflicient formaldehyde to equal about 0.25 percent formaldehyde based on the weight of said distillate.

5. The process as defined by claim 1 wherein said distillate boils in the range of from about 400 F. to 600 F.

7 References Cited in the file of this patent UNITED STATES PATENTS 1,998,292 Smith Apr. 16, 1935 2,011,199 Pelc Aug. 13, 1935 2,018,715 Fulton Oct. 29, 1935 2,068,850 Ellis Jan. 26, 1937 2,567,175 Arundale et a1. Sept. 11, 1951 FOREIGN PATENTS 289,920 Great Britain Apr. 30, 1928 

1. IN THE PROCESS OF PRODUCING A HIGH QUALITY PETROLEUM WHITE OIL WHEREIN A VIRGIN PETROLEUM DISTILLATE BOILING IN THE RANGE OF FROM ABOUT 300* TO 750*F. IS SUBJECTED TO A SUCCESSION OF SULFURIC ACID TREATING STEPS, THE IMPROVEMENT WHICH COMPRISES TREATING SAID DISTILLATE WITH 98 PERCENT SULFURIC ACID IN EACH OF SAID STEPS WITH THE EXCEPTION OF THE FINAL STEP, AND TREATING SAID DISTILLATE IN THE FINAL STEP WITH AN ACID MIXTURE COMPRISING MORE THAN ABOUT 90 PERCENT AND LESS THAN 98 PERCENT OF SULFURIC ACID, BASED ON THE WEIGHT OF SAID MIXTURE, AND FROM ABOUT 0.1 PERCENT TO ABOUT 0.4 PERCENT OF FORMALDEHYDE, BASED ON THE WEIGHT OF SAID DISTILLATE. 